Nordic ATWC Series, Installation And Service Manual, Page: 33 / 106

PRELIMINARY: 24-Sep-2021 Page 33 002536MAN-00
Heating setpoints will vary widely by application. Lower
indoor loop water temperatures may be able to be used, or high-
er ones may be required. Lower heating setpoints will translate
directly into a higher COP (efficiency). Increasing Delta values
will also increase efficiency due to longer runtimes, and lead to
less wear on compressor due to a reduced number of compres-
sor starts.
The maximum water temperature heating setpoint for the
cascade ATWC-series is 160°F / 71°C , while the minimum
setpoint for cooling is 45°F (7°C) . The heating setpoint is de-
rated at cold outdoor temperatures according to the following
table, to keep the compressors operating within their envelopes.
The de-rated setpoint will be shown as “ Actual SP ” in the Set-
point Control window. ( Actual SP will also be reduced by
the Outdoor Reset feature, described shortly.)
Top Up S1 Function
Enabling this feature allows the stage 1 setpoint to be
reached when the actual setpoint is de-rated due to the outdoor
temperature being cold (refer to previous table). When disa-
bled, the compressor(s) and stage 2 auxiliary operate normally
and shut off at their actual setpoints. When enabled, the heat
pump will shut off the compressor(s) at the actual setpoint as
usual. The auxiliary will now turn on (if already on, it will contin-
ue to be on) and continue up to the stage 1 setpoint. This cre-
ates a hybrid system that can maintain the stage1 setpoint even
when the heat pump is in de-rated mode for systems that need
hotter water than 145°F (63°C) at all times (although it may re-
sult in a significant portion of heat load on a cold day being met
by auxiliary heat only).
IMPORTANT NOTE: Do not enable unless auxiliary is oper-
ational, since if no auxiliary the compressor will never be re
re-enabled (as the setpoint will never be reached).
Summer Setback
In locations where hydronic cooling is not required, the
heating system may be idle for several months in the summer.
In this case, the heat pump may be put in Summer Setback
mode via the PC App’s Tools-->Configuration window or the
LCD Interface.
Summer Setback disables stage 2 (AUX), drops set-
points to 70°F (21°C), and decreases temperature sampling
frequency to 2 days. This minimizes electric power usage while
keeping cast iron head circulation pumps operational.
Hydronic Auxiliary in Defrost
AUX (stage 2) heat can be set to come on automatically
when the heat pump enters defrost mode via the PC App’s
Tools-->Configuration window.
This may be used to counter the cooling of the tank that
will occur during defrost. However, it is not normally required,
since changes in the buffer tank temperature of a short duration
will not be felt in most living spaces, and the temperature will
usually recover quickly after defrost.
TABLE 18 - Maximum Output Temperature
Outdoor
temp. °F
Max. output
temp. °F
Outdoor
temp. °C
Max. output
temp.°C
above 15°F 160°F above -9°C 71°C
11 to 15°F 155°F -11 to -9°C 68°C
6 to 10°F 150°F -15 to -12°C 65°C
below 6°F 145°F below -15°C 63°C
Click on
up/down
arrows to
adjust
setpoints
Indicators turn on
when a demand is
active
RED—heating
BLUE—cooling
WARNING: When in Manual Override mode, Activation
no longer responds to Setpoint Control values (i.e. if a
stage is on it will not turn off when the setpoint is
reached). Go to the PC App’s Control Panel to turn
demand ON/OFF with the Stage buttons.
The Setpoint Control window looks like this for Method 1 (Indoor
Loop - ICR):
Actual Setpoint
is reduced by
Outdoor Reset
Cold Setpoints
only visible for
reversing
models (HAC)
TABLE 17 - Typical ATWC-series Setpoints
HEATING
Stage 1 Stage 2 (Aux)
°F
°C
°F
°C
Setpoint 150
65
150
65
Delta 10
5
20
10
Activation * 140
60
130
55
Delay 10 minutes
COOLING
Stage 1
*Activation is
determined by the
Setpoint and Del-
ta values
°F
°C
Setpoint 45
7
Delta 8
4
Activation * 53
11